security: Add LSM hook to setgroups() syscall

Give the LSM framework the ability to filter setgroups() syscalls. There
are already analagous hooks for the set*uid() and set*gid() syscalls.
The SafeSetID LSM will use this new hook to ensure setgroups() calls are
allowed by the installed security policy. Tested by putting print
statement in security_task_fix_setgroups() hook and confirming that it
gets hit when userspace does a setgroups() syscall.

Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Micah Morton <mortonm@chromium.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/include/linux/security.h b/include/linux/security.h
index 7fc4e9f49f54..1dfd32c49fa3 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -415,6 +415,7 @@ int security_task_fix_setuid(struct cred *new, const struct cred *old,
 			     int flags);
 int security_task_fix_setgid(struct cred *new, const struct cred *old,
 			     int flags);
+int security_task_fix_setgroups(struct cred *new, const struct cred *old);
 int security_task_setpgid(struct task_struct *p, pid_t pgid);
 int security_task_getpgid(struct task_struct *p);
 int security_task_getsid(struct task_struct *p);
@@ -1098,6 +1099,12 @@ static inline int security_task_fix_setgid(struct cred *new,
 	return 0;
 }
 
+static inline int security_task_fix_setgroups(struct cred *new,
+					   const struct cred *old)
+{
+	return 0;
+}
+
 static inline int security_task_setpgid(struct task_struct *p, pid_t pgid)
 {
 	return 0;